Demi Lovato, Wilmer Valderrama Celebrate Sixth Anniversary

Demi Lovato and boyfriend Wilmer Valderrama are basking in the glow of their sixth year as a couple.

The 23-year-old "Confident" singer recently took to Instagram where she posted a montage of black-and-white photos marking each year she and the "That '70s Show" star have been together.

According to Us Weekly, Lovato started dating the now 35-year-old Valderrama when she was 17-years-old, just as she was embarking on one of the most sobering times of her life. Soon after they became a couple, Lovato entered rehab for substance abuse and mental health issues.

In a September cover story for Cosmopolitan, Lovato admitted she has been at fault for the only truly bumpy sections of their relationship, at one point briefly causing the couple to split.

"The only times we ever broke up were when I was relapsing, whether it was drugs or in a bad place and rebelling against everybody, not just him," she said. "People say that relapses happen before you use. Your mind starts setting up the relapse before you take that drink or that first hit. The times we'd broken up, I had already gone to that place of, 'Yeah, this is what's happening.' I didn't realize it at the time, but I just wanted to sabotage everything around me so that I could sabotage myself."

Nowadays, the celebs have become each other's primary support system, and their relationship appears to be flourishing. After remaining relatively private about their affairs, the two have opened up about their union in recent days, and they have become much more open in expressing affection for one another.

"We don't share everything with the world," Lovato said. "But we do feel comfortable to share a lot. With Wilmer and I and our relationship, he's extremely supportive in everything that I do. He makes me feel confident and beautiful. And I'm just really, really grateful for him."